Lifting jack



M. V..HL PERKINS.

LIFTING JACK.

APPLICATION FILED APR. 26. 1921.

1,403,812. Patented Jan. 17,1922.

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UNlTED STATES MARTIN V. H. .PERKINS, OF NEW YORK, N. Y.

LIFTING JACK.

Application filed April 26, 1921.

To aZZ 20710777. it may concern:

Be it known that l, MARTIN V. H. PnnnINs, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Lifting Jacks, of which the following is a specification.

This invention relates to lifting jacks of the type illustrated in the patent to Perkins 6: Patterson. No. I- 36. In said patent the base of the jack is provided with a vertical opening in which is arranged a lifting screw having a threaded engagement with a worm wheel, which latter is journaled upon the base and supports the lifting screw. By means of a worm engaging the worm wheel, the lifting screw may be raised, when restrained from turning by the load upon it, but will quickly return to its lowest position within the base when released from the load. In the jack of the aforesaid patent, the locking engagement of the worm with the worm wheel was relied upon to prevent backward rotation of the worm wheel by the downward pressure of the load, and this is possible where the pitch of the worm is not steep. lVith worms of steep pitch, however, it is desirable to have means for more positively locking the'worm and worm wheel against rotation by the pressure of the load, and the present invention comprises means whereby the worm shaft may be held against rotation so as to sustain the load at any desired height, or to raise or lower the load gradually, and this means is adjustable so as to release the worm and permit the load to descend rapidly when desired.

In the accompanying drawing,

Fig. 1 is a central, vertical section through the jack. the ratchet mechanism being shown in elevation, and the dotted lines representing a load upon the jack;

Fig. 2 is a detail view of the holding dog and its support, the worm shaft being shown in section on the line 22 of Fig. 4;

Fig. 3 is a section on the line 3-3 of Fig. 2;

Fig. l is a top plan view of the jack. with the top plate removed, the lifting screw being shown in section and the shaft casing and worm wheel being partly broken away;

Fig. 5 is an end view of the ratchet mechanism, showing the adjustment of the pawl and dog for raising the lifting screw and load; and,

Specification of Letters Patent.

Iatented Jan. 17, 1922.

Serial No. 464,542.

Fig. 6 is a similar view showing the adjustment of these parts for lowering the screw and load. step by step.

Referring to the drawing, A indicates a base or standard having a central, longitudinal opening 1., and having a socket 2 at its upper end. In this socket is arranged a worm wheel 3, the lower side of which rests upon ball bearings l. so that the wheel may turn with as little friction as possible in the socket. The hub of this worm wheel is elongated. as shown. and has a central threaded opening to receive a lifting screw 5. which turns freely in the worm wheel and is provided with a head 5 fixed to its upper end. The socket is enclosed by a suitable top plate 6. In an enlargement 2 of.the casing, at the side of the socket. is mounted, in ball bearings, a worm shaft 7, carrying worm S which engages the worm wheel. Upon one end of the shaft is arranged a ratchet wheel 9, having teeth 9 formed with radial faces and adapted to be engaged by a reversible pawl 10, mounted in a spring pressed slide 1 in a ratchet lever 12. The ends 10 and 10 of this pawl are oppositely inclined, and the pawl is provided with a knob 10, by which it may be turned to reverse its position with respect to the ratchet wheel.

The parts thus far described, except for minor details. are the same those described in the patent above referred to. In the lifting jack of said patent, the locking engagement of the worm with the worm wheel was relied upon to prevent rotation of the worm shaft by the weight of the load on the lifting screw; but with a steeply pitched worm, as shown in the drawing of the present case, the weight of the load on the lifting screw will cause rotation of the worm wheel and worm unless means is provided for preventing this rotation. I therefore provide teeth 13 on the worm shaft, these teeth being formed with radial faces, as shown, and on the end of the part 2 of the casing is mounted a support 14. which may be integral with the casing, for a reversible holding-dog l5, pivoted at 16 to the support and having at its lower end forked arms 15" and 15 which may be brought into engagement with the teeth 13 by rocking the dog from one of its extreme positions to the other. The plate 17 is secured to the end of the support 14 and has a notch l7 on its inner side which forms a guide for the dog. This plate has three holes or notches i8, 19, and. 20 on its inner side I adapted to be engaged by a spring pin 21 notch 19, holds the dog in this position.

IVhen the dog is moved to engage the arm 15 with the teeth, the pin enters the notch 18, and when the arm 15 is moved into engagement with the teeth, the pin enters the notch 20. 7

- lVith this type of jack, wherein the lifting screw turns freely in the hub of the worm wheel, the screw may be raised, without turning the ratchet mechanism and worm wheel, by turning the head 5 which is recured to the screw; but when the screw is released it will rotate in the worm wheel hub in the reverse direction and sink down until the head rests upon the top plate 6. Therefore, to lift a load, indicated by the dotted lines 21, the head 5 is turned by hand until it engages the load, such as a vehicle axle, and the engagement of the load with the head will prevent the screw from turning. To lift the load, the pawl 10 and the .dog 15 are set as shown in Fig. 5, and at each downward movement of the lever, the worm shaft will be turned through a part of a revolution and the worm wheel will be turned on the lifting screw, causing the latter to move upward and lift the load. The

arm 15" of the dog will engage the teeth 13 on the worm shaft and prevent backward rotation of said shaft between successive movements of the lever, and also after the load has been raised to the desired height;

descend by its own weight as soon as the head is relieved of the load, the screw turning in the worm wheel until the head reaches the top plate. 6. If it is desired to lower the load, step by step, or to hold it in any lower position, the dog and the pawl 10 are shifted into the positions shown in Fig. 6. Each upward pull on the lever will turn the worm and worm wheel one step in the direction to lower the lifting screw and load, and the arm l5 on the dog, by its engagement with the teeth on the worm shaft will prevent the worm shaft from being rotated by the weight of the load. This arm will slip over the teeth when the ratchet lever is'moved to turn the worm shaft in the direction to lower the load, but will press into the notches between the teeth with sufficient force to prevent free rotation of the worm shaft.-

lVhat I claim is: 1. In a lifting ack, a base, a lifting screw vertically arranged within the base, a worm wheel having a threaded engagement with said screw and having a bearing upon the base, a worm shaft having a worm engaging said wheel and having teeth, ratchet mechanism for rotating the shaft, and a dog adjustable into and out of engagement with said teeth.

2. In a lifting jack, a base, a lifting screw vertically arranged within the base, a worm wheel having a threaded engagement with said screw and having a bearing upon the base, a worm shaft having a worm engaging said wheel and having teeth, ratchet meohanism for rotating the shaft in either direction, and a reversible dog having two arms adapted to alternately engage said teeth in different positions of the dog.

3. In a lifting jack, a base, a lifting screw vertically arranged within the base, a worm wheel having a threaded engagement with said screw and having a bearing upon the base, a worm shaft having a worm engaging said wheel and having teeth, ratchet mechanism for rotating the shaft in either direction, and a reversible dog adjustable into three successive positions, said dog having two arms adapted to alternately engage said teeth in the extreme positions of the dog and to remain out of engagement with the teeth in its intermediate position.

In testimony whereof I afiix my signature.

.MARTIN v. H. rnmnns, 

